move contextlib2 into python_utils (oppia#12773)

.pylintrc

@@ -63,34 +63,37 @@ indent-string='    '
 
 allowed-comment-prefixes=int,str,float,bool,v
 forbidden-imports=
-    core.storage:core.domain,
+    core.controllers:core.platform|core.storage,
     core.domain:core.controllers,
-    core.controllers:core.platform|core.storage
+    core.storage:core.domain
 
 disallowed-functions-and-replacements-str=
-  now=>datetime.datetime.utcnow,
   assertEquals=>self.assertEqual,
-  StringIO=>python_utils.string_io,
-  urlparse.urlsplit=>python_utils.url_split,
-  urlparse.urlparse=>python_utils.url_parse,
-  urlparse.urlunsplit=>python_utils.url_unsplit,
-  urlparse.parse_qs=>python_utils.parse_query_string,
-  urlparse.urljoin=>python_utils.url_join,
-  urllib.unquote=>python_utils.urllib_unquote,
-  urllib.urlparse.unquote=>python_utils.urllib_unquote,
-  next=>python_utils.NEXT,
-  range=>python_utils.RANGE,
-  round=>python_utils.ROUND,
-  str=>python_utils.convert_to_bytes or python_utils.UNICODE,
-  zip=>python_utils.ZIP,
   basestring=>python_utils.BASESTRING,
+  contextlib2.ExitStack=>python_utils.ExitStack,
+  contextlib2.nullcontext=>python_utils.nullcontext,
+  contextlib2.redirect_stdout=>python_utils.redirect_stdout,
+  input=>python_utils.INPUT,
   iteritems=>items,
-  itervalues=>values,
   iterkeys=>keys,
-  print=>python_utils.PRINT,
+  itervalues=>values,
+  map=>python_utils.MAP,
+  next=>python_utils.NEXT,
+  now=>datetime.datetime.utcnow,
   open=>python_utils.open_file,
-  input=>python_utils.INPUT,
-  map=>python_utils.MAP
+  print=>python_utils.PRINT,
+  range=>python_utils.RANGE,
+  round=>python_utils.ROUND,
+  str=>python_utils.convert_to_bytes or python_utils.UNICODE,
+  StringIO=>python_utils.string_io,
+  urllib.unquote=>python_utils.urllib_unquote,
+  urllib.urlparse.unquote=>python_utils.urllib_unquote,
+  urlparse.parse_qs=>python_utils.parse_query_string,
+  urlparse.urljoin=>python_utils.url_join,
+  urlparse.urlparse=>python_utils.url_parse,
+  urlparse.urlsplit=>python_utils.url_split,
+  urlparse.urlunsplit=>python_utils.url_unsplit,
+  zip=>python_utils.ZIP
 
 disallowed-functions-and-replacements-regex=
   \.put_async\(=>put,

core/controllers/base_test.py

@@ -48,7 +48,6 @@
 import python_utils
 import utils
 
-import contextlib2
 from mapreduce import main as mapreduce_main
 import webapp2
 import webtest
@@ -555,7 +554,7 @@ def test_splash_redirect(self):
         self.assertEqual('http://localhost/', response.headers['location'])
 
     def test_unauthorized_user_exception_raised_when_session_is_stale(self):
-        with contextlib2.ExitStack() as exit_stack:
+        with python_utils.ExitStack() as exit_stack:
             call_counter = exit_stack.enter_context(self.swap_with_call_counter(
                 auth_services, 'destroy_auth_session'))
             logs = exit_stack.enter_context(
@@ -572,7 +571,7 @@ def test_unauthorized_user_exception_raised_when_session_is_stale(self):
             'http://localhost/login?return_url=http%3A%2F%2Flocalhost%2F')
 
     def test_unauthorized_user_exception_raised_when_session_is_invalid(self):
-        with contextlib2.ExitStack() as exit_stack:
+        with python_utils.ExitStack() as exit_stack:
             call_counter = exit_stack.enter_context(self.swap_with_call_counter(
                 auth_services, 'destroy_auth_session'))
             logs = exit_stack.enter_context(
@@ -598,7 +597,7 @@ class MaintenanceModeTests(test_utils.GenericTestBase):
 
     def setUp(self):
         super(MaintenanceModeTests, self).setUp()
-        with contextlib2.ExitStack() as context_stack:
+        with python_utils.ExitStack() as context_stack:
             context_stack.enter_context(
                 self.swap(feconf, 'ENABLE_MAINTENANCE_MODE', True))
             self.context_stack = context_stack.pop_all()

core/domain/auth_jobs_one_off_test.py

@@ -27,8 +27,7 @@
 from core.platform.auth import firebase_auth_services_test
 from core.tests import test_utils
 import feconf
-
-import contextlib2
+import python_utils
 
 auth_models, user_models = (
     models.Registry.import_models([models.NAMES.auth, models.NAMES.user]))
@@ -48,7 +47,7 @@ class SyncFirebaseAccountsOneOffJobTests(test_utils.AppEngineTestBase):
 
     def setUp(self):
         super(SyncFirebaseAccountsOneOffJobTests, self).setUp()
-        self.exit_stack = contextlib2.ExitStack()
+        self.exit_stack = python_utils.ExitStack()
         self.firebase_sdk_stub = (
             firebase_auth_services_test.FirebaseAdminSdkStub())
 

core/domain/state_domain_test.py

@@ -34,11 +34,10 @@
 from core.domain import translatable_object_registry
 from core.tests import test_utils
 import feconf
+import python_utils
 import schema_utils
 import utils
 
-import contextlib2
-
 
 class StateDomainUnitTests(test_utils.GenericTestBase):
     """Test methods operating on states."""
@@ -3842,7 +3841,7 @@ def test_validate_duplicate_content_id_with_solution(self):
     def test_cannot_convert_state_dict_to_yaml_with_invalid_state_dict(self):
         exploration = self.save_new_valid_exploration('exp_id', 'owner_id')
 
-        with contextlib2.ExitStack() as stack:
+        with python_utils.ExitStack() as stack:
             captured_logs = stack.enter_context(
                 self.capture_logging(min_level=logging.ERROR))
             stack.enter_context(

core/jobs_test.py

@@ -34,7 +34,6 @@
 import feconf
 import python_utils
 
-import contextlib2
 from mapreduce import input_readers
 
 (base_models, exp_models, stats_models, job_models) = (
@@ -232,7 +231,7 @@ def test_failing_jobs(self):
         job_id = MockJobManagerOne.create_new()
         store_map_reduce_results = jobs.StoreMapReduceResults()
 
-        with contextlib2.ExitStack() as stack:
+        with python_utils.ExitStack() as stack:
             captured_logs = stack.enter_context(
                 self.capture_logging(min_level=logging.ERROR))
             stack.enter_context(input_reader_swap)

core/platform/auth/firebase_auth_services_test.py

@@ -32,7 +32,6 @@
 import python_utils
 import utils
 
-import contextlib2
 import firebase_admin
 from firebase_admin import auth as firebase_auth
 from firebase_admin import exceptions as firebase_exceptions
@@ -115,7 +114,7 @@ def install(self, test):
 
         self._test = test
 
-        with contextlib2.ExitStack() as swap_stack:
+        with python_utils.ExitStack() as swap_stack:
             for name in self._IMPLEMENTED_SDK_FUNCTION_NAMES:
                 swap_stack.enter_context(
                     test.swap(firebase_auth, name, getattr(self, name)))

core/tests/test_utils.py

@@ -69,7 +69,6 @@
 import schema_utils
 import utils
 
-import contextlib2
 import elasticsearch
 from google.appengine.ext import deferred
 from google.appengine.ext import testbed
@@ -532,7 +531,7 @@ def install_stub(cls, test):
         Returns:
             callable. A function that will uninstall the stub when called.
         """
-        with contextlib2.ExitStack() as stack:
+        with python_utils.ExitStack() as stack:
             stub = cls()
 
             stack.enter_context(test.swap(
@@ -1844,7 +1843,7 @@ def run(self, result=None):
         es_stub = ElasticSearchStub()
         es_stub.reset()
 
-        with contextlib2.ExitStack() as stack:
+        with python_utils.ExitStack() as stack:
             stack.callback(AuthServicesStub.install_stub(self))
             stack.enter_context(self.swap(
                 elastic_search_services.ES.indices, 'create',

jobs/job_test_utils.py

@@ -20,6 +20,7 @@
 from __future__ import unicode_literals  # pylint: disable=import-only-modules
 
 import ast
+import contextlib
 import datetime
 import re
 
@@ -32,7 +33,6 @@
 from apache_beam import runners
 from apache_beam.testing import test_pipeline
 from apache_beam.testing import util as beam_testing_util
-import contextlib2
 
 
 class PipelinedTestBase(test_utils.TestBase):
@@ -52,7 +52,7 @@ def __init__(self, *args, **kwargs):
 
     def setUp(self):
         super(PipelinedTestBase, self).setUp()
-        with contextlib2.ExitStack() as stack:
+        with python_utils.ExitStack() as stack:
             stack.enter_context(decorate_beam_errors())
             stack.enter_context(self.pipeline)
             self._close_stack = stack.pop_all().close
@@ -187,7 +187,7 @@ def assert_job_output_is_empty(self):
         self.assert_pcoll_empty(self.run_job())
 
 
-@contextlib2.contextmanager
+@contextlib.contextmanager
 def decorate_beam_errors():
     """Context manager to improve the readability of beam_testing_util errors.
 

python_utils.py

@@ -60,6 +60,57 @@
 ZIP = builtins.zip
 
 
+def redirect_stdout(new_target):
+    """Returns redirect_stdout from contextlib2 if run under Python 2 and from
+    contextlib if run under Python 3.
+
+    Args:
+        new_target: FileLike. The file-like object all messages printed to
+            stdout will be redirected to.
+
+    Returns:
+        contextlib.redirect_stdout or contextlib2.redirect_stdout. The
+        redirect_stdout object.
+    """
+    try:
+        from contextlib import redirect_stdout as impl # pylint: disable=import-only-modules
+    except ImportError:
+        from contextlib2 import redirect_stdout as impl # pylint: disable=import-only-modules
+    return impl(new_target)
+
+
+def nullcontext(enter_result=None):
+    """Returns nullcontext from contextlib2 if run under Python 2 and from
+    contextlib if run under Python 3.
+
+    Args:
+        enter_result: *. The object returned by the nullcontext when entered.
+
+    Returns:
+        contextlib.nullcontext or contextlib2.nullcontext. The nullcontext
+        object.
+    """
+    try:
+        from contextlib import nullcontext as impl # pylint: disable=import-only-modules
+    except ImportError:
+        from contextlib2 import nullcontext as impl # pylint: disable=import-only-modules
+    return impl(enter_result=enter_result)
+
+
+def ExitStack(): # pylint: disable=invalid-name
+    """Returns ExitStack from contextlib2 if run under Python 2 and from
+    contextlib if run under Python 3.
+
+    Returns:
+        contextlib.ExitStack or contextlib2.ExitStack. The ExitStack object.
+    """
+    try:
+        from contextlib import ExitStack as impl # pylint: disable=import-only-modules
+    except ImportError:
+        from contextlib2 import ExitStack as impl # pylint: disable=import-only-modules
+    return impl()
+
+
 def string_io(buffer_value=b''):
     """Returns StringIO from StringIO module if run under Python 2 and from io
     module if run under Python 3.

scripts/run_e2e_tests.py

@@ -190,15 +190,12 @@ def build_js_files(dev_mode, deparallelize_terser=False, source_maps=False):
 
 def run_tests(args):
     """Run the scripts to start end-to-end tests."""
-    # TODO(#11549): Move this to top of the file.
-    import contextlib2
-
     if is_oppia_server_already_running():
         sys.exit(1)
 
     install_third_party_libraries(args.skip_install)
 
-    with contextlib2.ExitStack() as stack:
+    with python_utils.ExitStack() as stack:
         dev_mode = not args.prod_env
 
         if args.skip_build:

scripts/run_e2e_tests_test.py

@@ -24,6 +24,7 @@
 import time
 
 from core.tests import test_utils
+import python_utils
 from scripts import build
 from scripts import common
 from scripts import flake_checker
@@ -32,8 +33,6 @@
 from scripts import scripts_test_utils
 from scripts import servers
 
-import contextlib2
-
 CHROME_DRIVER_VERSION = '77.0.3865.40'
 
 
@@ -44,7 +43,7 @@ def mock_managed_process(*unused_args, **unused_kwargs):
         Context manager. A context manager that always yields a mock
         process.
     """
-    return contextlib2.nullcontext(
+    return python_utils.nullcontext(
         enter_result=scripts_test_utils.PopenStub(alive=False))
 
 
@@ -53,7 +52,7 @@ class RunE2ETestsTests(test_utils.GenericTestBase):
 
     def setUp(self):
         super(RunE2ETestsTests, self).setUp()
-        self.exit_stack = contextlib2.ExitStack()
+        self.exit_stack = python_utils.ExitStack()
 
     def tearDown(self):
         try:
@@ -277,7 +276,7 @@ def test_start_tests_when_no_other_instance_running(self):
 
     def test_work_with_non_ascii_chars(self):
         def mock_managed_protractor_server(**unused_kwargs): # pylint: disable=unused-argument
-            return contextlib2.nullcontext(
+            return python_utils.nullcontext(
                 enter_result=scripts_test_utils.PopenStub(
                     stdout='sample\n✓\noutput\n', alive=False))
 

scripts/run_lighthouse_tests.py

@@ -135,9 +135,6 @@ def run_lighthouse_checks(lighthouse_mode):
 
 def main(args=None):
     """Runs lighthouse checks and deletes reports."""
-    # TODO(#11549): Move this to top of the file.
-    import contextlib2
-
     parsed_args = _PARSER.parse_args(args=args)
 
     if parsed_args.mode == LIGHTHOUSE_MODE_ACCESSIBILITY:
@@ -161,7 +158,7 @@ def main(args=None):
         build.main(args=[])
         run_webpack_compilation()
 
-    with contextlib2.ExitStack() as stack:
+    with python_utils.ExitStack() as stack:
         stack.enter_context(common.inplace_replace_file_context(
             common.CONSTANTS_FILE_PATH,
             '"ENABLE_ACCOUNT_DELETION": .*',